This invention relates to a passenger conveyor system, and more particularly to a drive machine that restrains movement of the escalator tread plates.
A typical passenger conveyor, such as an escalator or moving walk, includes a frame, balustrades with movable handrails, tread plates, a drive system and a step chain for propelling the tread plates. The frame includes a truss section on both left and right band sides of the frame. Each truss section has two end sections forming landings, connected by an inclined midsection. The upper landing usually houses the escalator drive system or machine positioned between the trusses.
The drive system of an escalator typically consists of a step chain, a step chain drive sprocket, an axle and a drive motor. The drive motor drives the drive sprocket which imparts motion to the step chain. The step chain travels a continuous, closed loop, running from one elevation to the other elevation, and back. The step chain thereby propels the tread plates from one landing to the other. As the step chain engages the metal drive sprocket teeth, there is metal to metal contact which can produce noise.
Recently, escalators drive systems have incorporated a drive belt which engages the drive sprocket and the step chain. By driving the step chain with the drive belt, much of the metal to metal contact is eliminated which thereby reduces the potential for noise. However, should the drive belt not be engaged, the drive sprocket is no longer engaged with the step chain. The step chain, and thus the tread plates may be free to move.
Accordingly, it is desirable to assure that the step chain and attached tread plates are prevented from free movement independent of drive belt engagement.
An escalator system designed according to this invention improves escalator operational safety by providing a drive sprocket which are engageable the drive chain independently of a belt drive.
The escalator system includes a motor output sheave connected to a drive motor through a gearbox. The motor output sheave drives a drive belt along a closed loop between the output sheave and an idler sprocket. The belt engages with the step chain such that the step chain and attached tread plates are propelled from one landing to the other.
The output sheave preferably includes a first set of teeth and a second set of teeth. The first set of teeth is around a hub to engage a set of belt teeth extending from the drive belt. The second set of teeth is preferably located along a rim of the output sheave and are directly offset from the first set of teeth. The second set of teeth is engageable with corresponding link teeth located along each link in the drive chain. The second set of teeth maintain their relationship with the corresponding link teeth due to the first set of teeth, however, there is no contact therebetween. There is, therefore, no metal to metal contact during normal operation of the system. However, should the drive belt fail or become disengaged, the second set of teeth engage the corresponding link teeth. The step chain and attached tread plates are thereby prevented from moving independently.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.